Have you ever had the feeling that as you turned left, rather than turning right, your life took an entirely different direction?

That was exactly how Harriet felt, sitting in the heat of the day beneath a parasol as the wind gently buffeted it, sipping her chocolate and caramel frappuccino as mere feet away, cars and their angry, irate drivers were going nowhere fast.

There had been an accident, a hit and run apparently. A young mother and her child had been killed whilst crossing the road.

The thing is, Harriet had a sneaking suspicion that events had not played out quite as they were supposed to. In fact, she had a rather strong inkling that it was supposed to have been her, not the young mother and her child, who had fallen beneath the wheels of the car, apparently driven by an extremely cowardly individual.

"You're right, you know."

Harriet hadn't noticed the man sit down opposite her, which she found quite odd considering the man's attire. Surely she would have noticed that a man with incredibly dirty dreadlocks and tight-fitting body armour that looked as though it would protect its wearer from a close range nuclear blast, carrying what looked very much like a weapon capable of destroying a tank with nothing more than a tickle and the hilt of a sword protruding above each shoulder, sat down opposite her.

"I'm right?" she asked, thinking it was probably in her best interests to show politeness at the very least. "About what?"

"About the fact it was supposed to be you laying on the ground, dying of death after being hit by an Alfa Romeo doing seventy-three, give or take, in a built up area."

"How did you..?"

"Because I'm from the future," he replied, pausing to light a cigarette using a match struck upon the stubble of his chin. "Specifically, this future, 'cos until you didn't get killed in that hit and run, I didn't exist."

Harriet was confused, quite rightly, and she was well aware that her expression alluded to said confusion.

"I'm not surprised you're confused," the man said with a smile. "I'd wager that if I wasn't aware of the whole cause and effect malarkey, I'd be pretty confused as well."

"Cause and effect is simple enough to get my head around," Harriet replied. "What I don't understand is how my lack of death on this day makes any difference to whether or not you exist. I mean, are we related in some way?"

"No, nothing like that," he said with a shrug. "At this point in time, my closest living ancestors are a stripper working out of Las Vegas and an eleven year old schoolboy from Inverness."

Apparently she must of shot him a rather shocked expression because he hastily added, "don't worry, they don't get together for another ten years or so."

"Then I don't understand," she said, taking a brief pause to finish her frappuccino. "How does my continued existence influence your future existence?"

"Trust me, your continued existence influences a lot." Now it was his turn to pause once again, and stare directly at a man walking by who appeared to have taken interest in the arsenal of weaponry he was carrying.

"Move along, dickhead. Nothing to see here."

The interested man shrugged and shook himself, then went about whatever business he had that day. Later, it all came back to him and he spent hours and hours, trawling various online search engines in search of reference to a heavily armed man sitting outside a Starbucks in Central London, but found no such thing.

"Most people don't believe what their eyes tell them," he continued as he turned back to Harriet. "Most people, upon seeing all these weapons would simply assume it's their mind playing tricks... There's always one, though..."

"So my continued existence," said Harriet, thinking to herself how surreal the entire conversation was. "Is it a good thing?"

"Well that's a difficult question to answer," the man replied. "I mean, the history I've known is all that I've known. I have no idea what the world would have been like if you'd been hit by that car. All I know is what the world, my history, is like because you weren't hit by it."

"And what is your history like?"

"Bloody, brutal..." he replied, a faraway look in his eyes. "Lots of violence and war with a genocide or two thrown in for good measure."

"Oh my..."

"Hey it's not all bad," he replied with a half-smile. "Trust me, we've got some bitchin' water parks where I'm from and the music is pretty damn sweet, too."

"I'm not sure water parks and decent music compensates for genocide..."

"Clearly you've never been to Splatter Canyon," he replied with a chuckle.

"Clearly..."

He shrugged and lit another cigarette from the still-smouldering tip of the other.

"So I suppose you're going to tell me I should make the most of my life, considering I wasn't supposed to live past this morning."

"I'm not going to tell you anything," the man replied. "Your life is yours to do with what you will and it doesn't matter what that is. Most of what you do won't affect the future in any way whatsoever."

"Most?"

"Aye, most... It's a bit of a misnomer, really, that every single decision we make creates a different future. 'Course, some decisions do."

"Like my decision to turn right instead of left?"

"Exactly," he replied. "Sure, it might not have felt like a big decision at the time but those life-changing decisions don't have to be big, they just have to be."

"Do you know which decisions are going to affect what?"

"No, and I wager that's no bad thing. Can you imagine the power anyone who knew that would hold?"

"I suppose..."

"It'd make the Venusian Wars look like an astrobar brawl... It'd be..." he cut himself short, and shuddered.

"Well we couldn't have that, could we?"

"No, we couldn't," he replied. "I lost a lot of good friends down on Venus... It was a massacre..."

"And that massacre happens because I didn't get hit by that car?"

"Indirectly but yeah, sure, and to be fair not for a few hundred years so you probably shouldn't hold yourself responsible."

"So time travel, too?"

"What about it?" he asked. "You're asking if you're indirectly responsible tor time travel?"

The man released the most almighty guffaw, slapped the table reasonably hard and wiped tears from his eyes before he continued.

"I'm sorry," he said, attempting quite unsuccessfully to stifle further outbursts. "I'm sorry, but no. Time travel was cracked decades ago."

"Who by? Hawking? Einstein?"

"None of the above. I don't suppose the name Freddie King means anything to you?"

"Not a thing..."

"I didn't expect it would... What are we, twenty fifteen? Give it about fifteen years and he'll show up claiming to have spent three weeks living with a family of Neanderthals."

"Neanderthals... Wait, you don't mean..?"

"That's exactly what I mean," he replied. "All the evidence that shows Neanderthals and Homo Sapiens getting it on, that's King."

"I can't even..."

"I know, I know," he replied, kindly. "It's a lot to get your head around."

"Yeah, it is," said Harriet. "Listen, I think I need to go for a walk, stretch my legs and try and sort all of this out in my mind."

"That's understandable," he replied. "I reckon I'd have to do the same."

"It was lovely to meet you, erm, I'm sorry I never got your name."

"I didn't give it," he replied with a smile, "but it was nice to meet you too, Harriet."

With a slightly befuddled grin she got to her feet, turned and made to walk away. She did not get very far though because as she turned, the man stood and drew one of his swords. Bringing it around in a beautifully executed arc he severed Harriet's head from her neck. Both body and head fell to the ground with a dull thud, landing mere inches apart.

"Just because you didn't die beneath the wheels of that Alfa Romeo today doesn't mean that you weren't supposed to die," he said, quietly. "I'm sorry, Harriet, I truly am, but your survival this morning has already done too much damage. We can't risk your continued existence influencing our history even more."